title: From tetragermacyclobutene to tetragermacyclobutadiene dianion to tetragermacyclobutadiene transition metal complexes.
abstract: The reaction of 3,4-dichlorotetragermetene derivative 2 with Na(2)[Fe(CO)(4)] in THF produced a (tetragermacyclobutadiene)tricarbonyliron complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]Fe(CO)(3)4, which has a slightly folded Ge(4) ring perhaptocoordinated to the Fe center. Structural and spectral characteristics of 4 show a remarkable π-donating ability of the tetragermacyclobutadiene ligand toward the transition metal, surpassing that of tetrasilacyclobutadiene and cyclobutadiene ligands. Reduction of 2 with KC(8) resulted in exclusive formation of the dipotassium salt of the tetragermacyclobutadiene dianion derivative 3(2-)·[K(+)(thf)(2)](2), representing a rare example of a 6π-electron compound that, on the basis of its structural and magnetic properties, was recognized as a nonaromatic species. Reaction of 3(2-)·[K(+)(thf)(2)](2) with CpCoI(2)(PPh(3)) produced a (cyclopentadienyl)(tetragermacyclobutadiene)cobalt complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]CoCp 7, as the first example of a sandwich compound featuring an all-germanium-containing cyclic polyene ligand.
authors.affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Vladimir Ya
authors.initials: VY
authors.lastname: Lee
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ito
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yasuda
authors.forename: Kazunori
authors.initials: K
authors.lastname: Takanashi
authors.forename: Akira
authors.initials: A
authors.lastname: Sekiguchi
mesh_terms: D000838:Anions / Q000138:chemical synthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D003503:Cyclobutanes / Q000138:chemical synthesis* / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D000838:Anions; D003503:Cyclobutanes; D009942:Organometallic Compounds; D028561:Transition Elements